Fix hard-crash when opening background links from PWA windows.

See bug for full description.

Now if a tab wants to open another tab in the same group, but the other
tab would open in a different window, the group is not assigned. Calling
TabStripModel::InsertWebContentsAt() with params specifying a group that
does not exist at all in the tabstrip is (and should be) an invalid
operation.

Bug: 1011140
Change-Id: I34d9cf15ec74b96f9c5c53878f76f124fcca4d57
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1839015
Commit-Queue: Peter Boström <pbos@chromium.org>
Reviewed-by: Peter Boström <pbos@chromium.org>
Auto-Submit: Dana Fried <dfried@chromium.org>
Cr-Commit-Position: refs/heads/master@{#703458}

chrome/browser/ui/browser.cc

@@ -2447,6 +2447,9 @@ void Browser::ConfigureTabGroupForNavigation(content::WebContents* source,
   if (!source)
     return;
 
+  if (!SupportsWindowFeature(WindowFeature::FEATURE_TABSTRIP))
+    return;
+
   const int source_index = tab_strip_model_->GetIndexOfWebContents(source);
 
   // If the source tab is pinned, don't create a group.